Re: [escepticos] Vacas locas-Lo que se sabe

[calvoreb@...>]

Información que acaba de pasar J. Pablo Zamorano en la lista de CYTALI.
Creo que puede ser interesante para todos. Si es verdad es todo un golpe








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Nature Science Update http://helix.nature.com/nsu/001123/001123-8.html


Blood test for prions?
DAVID ADAM
Researchers in Austria and Switzerland have taken a significant step towards
developing a reliable test for diseases such as BSE. They have discovered
that acommon blood component sticks to the rogue prion proteins causing
these diseases, but not to similar, non-infectious versions.
The discovery offers new clues about how prion diseases progress, and could
even sweep clean infected blood products for transfusions.
Adriano Aguzzi of the University Hospital of Zurich, Switzerland and his
colleagues used the protein ?plasminogen? from human and mouse blood serum.
They coated tiny magnetic beads with the sticky protein and mixed them with
samples of brain tissue from mice infected with the sheep disease scrapie.
Scrapie is caused by a build-up of a prion protein called PrPSc, a corrupt
version of a natural protein called PrPC.
When they retrieved the beads with a magnet, the team found that the protein
coat was bristling with the infectious PrPSc prions, but not with the
non-infectious PrPC version.
The researchers also used the beads to selectively retrieve PrPCJD prions
from the brain  tissue of human CJD victims. They report their results in
Nature.
This is the first time that scientists have identified a substance in the
blood that
distinguishes between diseased and healthy prion proteins. This could be
crucial to understanding how diseases like BSE and CJD kill their victims.
As the disease takes hold, corrupt prions are believed to force healthy
proteins to fold into shapes that the body cannot break down.
But the accumulation of diseased, spongy prion deposits alone cannot explain
all the symptoms of prion diseases. "PrPSc probably damages the brain by
interacting with other cellular constituents," Aguzzi?s team explains.
Plasminogen could be one of these. Because the plasminogen-coated beads can
retrieve infectious prions for analysis, the technique could be used to
identify prion diseases at an early stage. Currently, prions can only be
identified in brain tissue after death. Entire herds of cattle have been
slaughtered to prevent the spread of BSE, for example, because there is no
way of knowing which cows were actually infected.
Could using plasminogen allow BSE to show up in a simple test while the
animal is still alive? "It is too early to tell," says Christiane Roeckl,
one of the Zurich team. "At the moment this is just a biochemical finding,"
she explains. "We just don?t know how sensitive the binding could be."
Theoretically, the coated beads could help to remove infectious prions from
blood products, she adds. Nobody is really sure if prion diseases can be
transmitted through blood transfusions, but the US bans donors who have
lived in the UK as a precaution following the BSE crisis.
"If these data are confirmed then it seems we have a new and potentially
powerful tool," says Pierluigi Gambetti, a prion researcher at Case Western
Reserve University, Cleveland, Ohio. "The ability to remove diseased prions
and leave behind healthy versions will be particularly useful," he adds.

Fischer, M. B. et al. Binding of disease-associated prion protein to
plasminogen. Nature 408, 479?483 (2000).


Miguel Calvo
Tecnologia de los Alimentos
Facultad de Veterinaria. Universidad de Zaragoza
Miguel Servet 177
50013 Zaragoza
Spain